A Preliminary Geoseismological Report on Kashmir Earthquake of 8th October 2005 Geological Survey of India, Northern Region A devastating earthquake shook the western Himalaya and adjoining regions on the morning of 8 th October 2005, inflicting very heavy casualties in a large area, particularly belonging to the Pak Occupied Kashmir (POK). This deadliest of the Himalayan earthquakes recording a magnitude of 7.6 took a toll of thousands of human lives and rendered millions homeless. The human death figure on the Indian side of the LOC crossed 1300 where as in the POK it is reported that nearly 50,000 people perished in the catastrophe. The epicentre of the event was located in the Kishanganga (Neelam) valley, north of Muzaffarabad in POK, some 125 km WNW of Srinagar (Fig.1). The USGS web site gave the following parameters of the 8 th October main event on 8 th October 2005. Date: 05/10/08 Origin Time: 03: 50: 38.63 (UTC) Epicentre: 34.432 ° N: 73.537 ° E Mw: 7.3 Depth: 20 km Best Double Couple Solution Seismic Moment: Mo = 1.0 x 10 20 Nm NP1: strike = 358 ° , dip = 29 ° , slip = 140 ° NP2: strike = 124 ° , dip = 72 ° , slip = 67 ° The USGS recorded 22 aftershocks of M ≥ 4.5 in the first eighteen hours of the main shock. IMD Parameters Origin Time:03 hr 50 min 35.8 sec Epicentre: 34.6°N:73.474°E Magnitude: 7.4 The Broadband Seismological Observatory of GSI at Jabalpur also recorded the main event and evaluated the origin time as 03 hr 50 min 56 sec. The short period MEQ digital recorders stationed at GSI Office, Chandigarh for purpose of seismic microzonation of the urban complex gave the following attributes of the earthquake. Arrival time of P-wave: 03: 51 : 51.27 (GMT) Time gap between arrival of P and S waves (S-P): 55.08 seconds Signal duration at Chandigarh: 15 minutes Epicentral distance of the earthquake from Chandigarh: 496 km (approx). A three-station MEQ network operating at Chandigarh recorded as many as 160 aftershocks till 11.30 hrs of 10.10.2005. A TV News Channel of Pakistan reported occurrence of th and 14 th October 2005. The date-wise distribution of numbers of 575 aftershocks between 8 the aftershocks during this period was 102, 122, 75, 76, 63, 78 and 59, respectively. 1
The Geological Survey of India, Northern Region has taken up the investigation o f the earthquake in a big way. Officers from Operations P&H.P, J&K and Uttaranchal, apart from Earthquake Geology and Landslide Hazard Studies Divisions, have been pressed in to service to collect data pertaining to the effects of the earthquake from different places with the main objective of constraining the isoseismals of this mega seismic event. It is planned to establish an array of three short period digital MEQ seismographs in the Kashmir valley to record the aftershock activity, which has so far been very prolific. A number of M ≥ 5 aftershocks, which can be felt even at far off places, are still occurring at quite a regular interval. Seismotectonic Setup The epicentre of the earthquake is located in the Frontal Himalayan Belt and is bounded in the north and east by the Main Boundary Thrust (MBT) and in the west by Jhelum and Shinkiari Faults (Fg.1). Represented by the cover rocks of the Frontal Belt affected by fold-thrust movements during the terminal phase of Himalayan orogeny, the epicentral tract lies in the Jhelum re-entrant, which is the outer reflection of the Great Western Himalayan Syntaxis. Jhelum fault is a prominent N-S trending tectonic discontinuity showing left lateral movement. It separates the Kashmir and Peshawar tectonic basins and has registered neotectonic activity. The Shinkiari fault is a sub-parallel neotectonic feature marking the eastern boundary of the Peshawar basin. It is to be mentioned here that one of the nodal planes of the USGS fault plane th October 2005 earthquake has almost a N solution of the 8 -S strike, paralleling the Jhelum- Shinkiari fault system. The last 120-year database on the seismicity of the region indicates occurrence of many earthquakes of M ≥ 4 in the Kashmir basin. Of these, the earthquake of 30 th May 1885, with its epicentre located 19.5 km west of Srinagar, was the most powerful. This earthquake caused nd September 1963 Badgam widespread damage, in which 3000 human lives were lost. The 2 earthquake of Mb 5.1 also caused some low order damage in the Kashmir valley. Damage Survey in Kashmir Valley The epicentre of the earthquake is located north of Muzaffarabad in the Neelam valley in the POK. As per the reports, the damage has been of a very high order in the Muzaffarabad- Balakot sector, where thousands of people are reported to have perished. During the course of the present survey some 15 localities were visited in the Kashmir valley to observe the effects of the earthquake. The place wise description follows. Srinagar Town The tremors, accompanied by a whizzing sound, were very strong at Srinagar town. There was lot of panic all around and some, particularly women and children, remained traumatized for days. It was difficult to stand, so people sat down, and some, to maintain balance, kneeled on the ground. During the earthquake, those driving two or four wheelers felt the shocks and immediately came to a halt in panic. At Srinagar, damage to the buildings and other civil structures were not significant. In Batmaloo area, partial collapses of a few old and weak brick walls could be seen (Photo 1). In a very old building constructed of unbaked bricks with timber reinforcement, a staircase collapsed. In the Hazaratbal Shrine a few marble face stones got peeled off from a burzi under the influence of the strong tremors (Photo 2). Cracks appeared in many structures in the down town area. Grade 1 cracks could be seen in some well-constructed buildings as well. The Shankaracharya Temple, situated over a Panjal Volcanics hilltop, remained unscathed. This 2
ancient structure, repaired and renovated in parts in recent times, is founded over solid bedrock and is constructed of large tabular basalt blocks having very good shear strength. It was perhaps the type of construction, which prevented any damage from taking place in a zone of fairly high intensity of shaking. In Srinagar town, most of the new constructions are generally of two stories and have used reinforced bricks with sand-cement mortar in the walls and G.I. sheets in the slanting roofs. These structures escaped without any significant damage. Baramula Town The town of Baramula is located on the banks of Jhelum River over Karewa deposits, comprising sand, silt and clay. The tremors, accompanied by a sound of blowing storm, were very distinct, instilling a deep sense of fear among the residents. The tremors were described to be having a predominant E-W horizontal direction of vibration under whose influence several of the civil structures came under distress. Some of the low compound walls, constructed of stone masonry packed in mud mortar, failed during the earthquake. A few of such buildings also suffered partial collapse. Many of the buildings developed cracks and plaster peeling off from places. A portion of a well-constructed, two story brick structure, housing the Dayal Furnisher Show Room, caved in and the ground floor brick wall developed gaping diagonal shear cracks (Photo 3). It appears that the lean brick columns supporting the rather heavy structure were not capable of withstanding the strong horizontal seismic loading, and thus failed. The building is founded on silty soil where groundwater occurs at a depth of 7.5 m. Rampur-Uri Sector As one proceeded west of Baramula, a perceptible increase in the intensity of ground motions was witnessed. The gate of Rampur Garrison was found sheared with its plaster peeled off at places. Further ahead along the Muzaffarabad highway, the ancient temple of Buniyar, also known as Pandav Temple, constructed in the 12 th Century AD by the Rulers of Avantivarman Dynasty, suffered some conspicuous damage on account of the earthquake. From its high front portal, some of the large interlocking blocks of granite slipped off and were seen strewn by the side of the road (Photo 4). The sanctum sanctorum of the rather dilapidated temple developed gaping cracks. The Datta Mandir near Mohura of a similar architecture as that of Buniyar temple but constructed of large blocks of metavolcanics suffered partial collapse in one corner (Photo 5). The pitched stones from the retaining walls were also dislodged. The dwellings of the nearby settlements were appreciably damaged and their inhabitants had shifted in makeshift tents adjoining the Temple precincts. The failure of terrace slopes of Jhejum valley was first spotted near Mohura (Photo 6). Near Bandi, a debris slide that blocked the Highway was triggered by the strong tremors of 8 th October 2005. At Uri, there was a clear accentuation in the intensity level as from here onwards, most of the structures suffered Grades 4 and 5 damage (Photo 7). In this intensity zone, large-scale collapse of the dwellings and fairly intense coseismic slope failures were responsible for a number of deaths and injuries. Uri-Kamalkot Sector The village of Salamabad, situated about 6 km from Uri along the Muzaffarabad Highway, was totally destroyed by the earthquake. Here, most of the structures, constructed of 3
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